outdoor sump for fifth wheel trailer.

My neighbour lives in his fifth wheel trailer. He developed a sewage problem that is puzzling us both. He has no computer.

All sewage from his trailer holding tank is piped to an outdoor sump some distance away, and below the level of the trailer.

This sump is like a large plastic bucket about 2ft diameter by 3ft high. It contains a pump with float switch, and a PVC check valve above the pump. This 2 inch PVC then continues to his sister's septic tank some 50ft away. Apart from thread to the pump, everything is glued.

Everything has worked well in the three years since installation. Until, that is, a week ago. We had an unusual cold spell for a few days to minus 10 C (about 14 F). The effluent in the sump, as well as in the PVC unburied section outflow line froze, and burst the line between the trailer and the sump. All this was discovered when the temperature rose, and the contents of the septic tank above the trailer's output line drained out. Not knowing at this time exactly what was happening, he unplugged the power to the sump pump. When things slowed to a drip, my neighbour taped the cracked line with duct tape, which made a good temporary seal.

He then transferred some effluent from his holding tank to the outside sump, which made the pump turn on (normal hum was heard), but pumpout was not happening.

He unbolted the cover and lifted the pump and check valve assembly out of the sump and placed it outside. Nothing was obviously wrong from the outside. Power was reconnected. Manual lifting of the float switch turns the pump motor on. Inspection through bottom hole confirms that impeller is spinning. Assembly was returned to sump, and repowered. Since float was up, pump turned on, but effluent level didn't change after a minute, so power was removed.

What could be wrong? Could the freezing have damaged the check valve to cause it to be stuck in the closed position? Could a pin be sheared between motor shaft and impeller so that the impeller slips?

Thanks, hj for responding. Actually, we've now been having a warm spell, so everything is thawed. Still no flow. Additionally, whoever installed this glued everything, so there's no union. Luckily, there's no flow into the septic tank from the sister's house (gone to warmer climate for a month). and the delivery pipe has now completely drained itself, drop by drop, via the duct taped crack repair.

I guess I'll advise my neighbour to cut and cap the septic tank side of the pipe, then power on. If no flow, as I'm sure will be the case, then the check valve will have to be cut out (though I can't really see it as causing a blockage - but I'm no pro plumber). Then, try the pump by itself, which, I'm afraid will also be a no go. Do these units have shear pin between shaft and impeller, or is there a key or a press fit? Does anyone know? Pump make and model is completely unreadable on rating plate.

My previous post stated something like three years since installation. This, apparently, was wrong. My neighbour says it's been over nine years!

Finally, if the shaft/impeller interface is indeed slipping, I can see a very labour intensive pump repair as opposed to a new pump with a new warranty (and I'm NOT interested in doing the repair, I'm too squeamish!)